A news article doesn't explain WHY in the headline, it explains what.
In this case, the OP's first line is spot on... if you're reading through git log, you can see that this commit likely didn't change anything functional about a test, and you should move on.
There's little reason to search the text of commit messages to find out what changed. There are many git tools to find out which commits affected parts of the code you're interested in. Whereas, trying to find that in commit messages is really inefficient and relies on reading, rather than such automated tools.
The purpose of the commit message is to help our fellow humans get a higher level understanding than is available from quickly scanning the code.
We already know what changed: it's the diff! We need to know why you're making the what.
The message should address why the diff is necessary. Was it a bug fix? Ok, what's the bug you're fixing? What's the evidence that you think they diff addresses it? Is it a new feature? What's the requirement? I can already tell what you did by the diff, but I can't tell from the diff alone if it actually matches the requirement!
I've always used it as a summary, so I can understand what has been done when browsing the history. It allows me to find changes that I want to cherry-pick or revert. OTOH I can see benefit of describing why a change was done as the summary, as then git blame on the line is a lot more effective.